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For the long-term preservation of the genetic resources of endangered fish species, a combination of germ cell cryopreservation and transplantation can be an effective technique. To optimize these techniques, it is important to identify undifferentiated germ cells possessing transplantability, such as primordial germ cells, type A spermatogonia (ASGs), and oogonia. In this study, a homolog of vasa cDNA in Mekong giant catfish (MGC-vasa) (Pangasianodon gigas), which is an endangered species inhabiting the Mekong river, was cloned and characterized for use as a putative germ cell marker. Results indicate that MGC-Vasa contained all of the consensus motifs, including the arginine-glycine and arginine-glycine-glycine motifs, as well as the nine conserved motifs belonging to the DEAD-box family of proteins. Results from phylogenetic analysis indicated MGC-vasa also grouped with Vasa and was clearly distinguishable from Pl10 in other teleosts. Results from analysis of abundance of mRNA transcripts using reverse transcription-polymerase chain reaction and in situ hybridization performed on immature Mekong giant catfish testis indicated vasa was present specifically in germ cells, with large abundances of the relevant mRNA in spermatogonia and spermatocytes. Sequence similarity and the specific localization of MGC-vasa in these germ cells suggest that the sequence ascertained in this study was a vasa homolog in Mekong giant catfish. Furthermore, vasa-positive cells were detected in prepared smears of testicular cells, indicating that it may be a useful germ cell marker for enzymatically dissociated cells used for transplantation studies.

Aquatic resources in Thailand have been affected by the introduction of Amazon sailfin catfish, Pterygoplichthys pardalis. This species has had a negative impact on native fish and has not been caught and consumed widely. At present there is debate as to whether it will be best to remove them from natural water sources or find some way to gain benefits from the presence of this species in Thailand. This research was conducted to evaluate the possibility of replacing standard fish meal with P. pardalis meal in the diets of juvenile Mekong giant catfish, Pangasianodon gigas. Five diets with replacement levels of 0% (control), 25%, 50%, 75% and 100% were tested for 90 days. The results showed that the weight gain (WG), average daily growth rate (ADG), specific growth rate (SGR), feed conversion rate (FCR), feed efficiency (FE) and protein efficiency ratio (PER) were not significantly different when compared with the control group. In none of the groups mortality occurred. Moreover, serum biochemistry indices such as levels of alanine aminotransferase (ALT), aspartate aminotransferase (AST), glucose, albumin, globulin, protein, triglyceride and cholesterol were not significantly different from the control group (ANOVA, p > 0.05). Based on our results, we conclude that commercial fish meal can be replaced with P. pardalis meal to make up 100% of the diet of P. gigas without producing any adverse effects on growth performance, feed utilization and serum biochemical indices. Keywords: Aquaculture, Fish meal replacement, Formulated feed, Growth performance, Serum biochemistry

The Mekong Giant Catfish, Pangasianodon gigas, is of great cultural importance for people in Southeast Asia. Over the past century, the population of the species has dramatically declined. Several conservation measures have been taken such as establishing laws to ban catching, conserving the known spawning ground and setting up captive breeding programmes. Interestingly, the captive-bred Mekong Giant Catfish now seems to outnumber the wild population. Detecting the presence of the species is essential but conventional approaches have several limitations. Environmental DNA (eDNA) analysis was used here to detect the Mekong Giant Catfish in the Chao Phraya River basin and reservoirs in the basin. The results from this study clearly show that the eDNA of the Mekong Giant Catfish were found concentrated in the large reservoirs. The concentration of the eDNA of the Mekong Giant Catfish was found to vary among the sites which range from around 31.0–116.8 copy numbers per ml. The Mekong Giant Catfish's eDNA was not detected in water collected from the upstream rivers of the reservoirs but found in the downstream samples. The results reflect those reports of catching the species by locals in the areas. The eDNA detection was proved here to be one of the most efficient, rapid and sensitive methods for the Mekong Giant Catfish monitoring and is now ready to be used if need be.

Dams development in Lower Mekong Basin (LMB) can help mitigate regional energy crisis and improve resilience to global extreme events. However, the trade-off can produce various risks, particularly to aquatic environment as transboundary impacts. The Xayaburi dam has been constructing in LMB and will be completed in 2019. We revealed several tangible environmental changes such as water level and riverbank. Actual field survey was conducted from 2014 to 2016 with local participation. Local people informed that risk caused by the construction and part operation of the dams. As water level was unregulated then fish stock change and agricultural area along riverbank were destroyed because of unforeseen flood. Local tourism sites also obtained risk from rapid and immediate high level of water with sediment contamination. River island and riverbank ecosystem also have been degraded, which has negatively affected migration birds and fish habitat. The number of wild Mekong giant catfish is reduced and lately will be subjected to extinct status. Thus, transboundary environmental impacts have to be considered from all levels of stakeholders using education and communication as soft intervention. The potential environmental and geopolitical risks of dam development required appropriated monitoring system associated with social engagement units to sustain LMB environment.

The larviculture of Mekong giant catfish (Pangasianodon gigas, Chevey 1930) solely relies on live feeds.This study aimed to investigate the proper time to replace live feeds with a microcapsule diet (MC diet) in the earliest stage of larvae to reduce dependency on live feeds in larval rearing of Mekong giant catfish. Crude enzyme of the 3-dph (days post hatching), 7-dph, 14-dph, and 30-dph larvae were extracted for determination of proteolytic digestive enzyme activities. Specific activities of total protease, chymotrypsin-like and trypsin-like of larvae displayed an elevated tendency with increasing life stage of larvae. The highest specific activities of all digestive enzymes were noticed at 30 dph (p 0.05). Feeding MC diet did not cause any histopathological alterations in liver and intestine of catfish. In conclusion, early introduction of catfish larvae with MC diet alone can start at 30 dph, which helps in shortening Moina feeding period, providing growth rate and survival rate benefits.

Pressures on freshwater biodiversity in Southeast Asia are accelerating, yet the status and conservation needs of many of the region’s iconic fish species are poorly known. The Mekong is highly species diverse and supports four of the six largest freshwater fish globally, three of which, including Mekong giant catfish (Pangasianodon gigas), are Critically Endangered. Emerging environmental DNA (eDNA) techniques have potential for monitoring threatened freshwater biodiversity, yet have not been applied in complex and biodiverse tropical ecosystems such as the Mekong. We developed species-specific primers for amplifying Mekong giant catfish DNA. In situ validation demonstrated that the DNA amplification was successful for all samples taken in reservoirs with known presence of Mekong giant catfish independent of fish density. We collected water samples from six deep pools on the Mekong, identified through Local Ecological Knowledge, in Cambodia, Lao PDR, and Thailand. DNA was extracted and amplified from these samples using the designed primers and probes. Mekong giant catfish DNA was detected from one sample from the species’ presumed spawning grounds on the Mekong mainstream, near the border between northern Thailand and Lao PDR. eDNA sampling using species-specific primers has potential for surveying and monitoring poorly known species from complex tropical aquatic environments. However accounting for false absences is likely to be required for the method to function with precision when applied to extremely rare species that are highly dispersed within a large river system. We recommend that such approach be utilised more widely by freshwater conservation practitioners for specific applications. The method is best suited for baseline biodiversity assessments or to identify and prioritise locations for more rigorous sampling. Our methods are particularly relevant for systems or species with limited baseline data or with physical characteristics that logistically limit the application of conventional methods. Such attributes are typical of large tropical rivers such as the Mekong, Congo, or Amazon.

The Mekong giant catfish Pangasianodon gigas is one of the largest freshwater fish, measuring up to 3 m in total length. This study was designed to determine the feeding habits of P. gigas to better understand how the fish achieve their large body size. We compared the relationship between gut length (GL) and total length (TL) among related species in superfamily Bagroidea, order Siluriformes (Pangasianodon hypophthalmus and Hemibagrus nemurus) in the Kaeng Krachan reservoir, Thailand. The mean relative gut length (RGL = GL / TL) of P. gigas was 3.50, showing that they have relatively long guts, with values more similar to those of omnivorous P. hypophthalmus (RGL = 3.70) than to those of carnivorous H. nemurus (RGL = 0.92). In the allometric relationship (i.e., log10 GL = log10 a + b log10 TL), the slope close to 1 for P. gigas (b = 1.07) has been widely observed in carnivores, while P. gigas has a greater intercept of the linear equation than P. hypophthalmus and H. nemurus, resulting in a similar GL of P. gigas to omnivorous P. hypophthalmus at approximately 35 cm in TL. Moreover, GL of P. gigas at 150 to 250 cm in TL showed great variations (RGL = 1.35-6.32). The variation in RGL for P. gigas seemed to result from a poor nutritional state. In conclusion, P. gigas is suggested to feed on indigestible materials such as plants, algae, and sediments, and potentially experience fasting in a reservoir.

The horizontal and vertical movements of eight immature hatchery-reared (F2) Mekong giant catfish Pangasianodon gigas were monitored using acoustic telemetry in the Mae Peum reservoir, Thailand, from September to December 2005. All tagged fish were successfully monitored throughout the study period. All fish moved throughout the reservoir for approximately 1 month after release. Subsequently, their utilized areas became small, and the fish utilized deep areas of the reservoir. The fish displayed diel spatial movement patterns between deep areas in the day and shallow areas in the night. The vertical movements of the fish were related to the environment declination such as existence of hypoxic water and thermocline. Our results suggest that the establishment of a protected area in addition to conventional fisheries regulations may sustain the fish population in this reservoir.

Twenty-eight immature hatchery-reared Mekong giant catfish Pangasianodon gigas tagged with acoustic transmitters were released in the Mekong River, Thailand from 2002 to 2004. Twenty-four and four fish were tagged with normal transmitters and pressure-sensitive transmitters, respectively. Five to seven automated monitoring receivers were used for monitoring the post-release movements. The tagged catfish could be detected for up to 97 days, the first detection taking place at the release point, where the fish remained for several days. Sixteen tagged fish (57%) were not detected at any later point. These fish may have passed along the opposite (Laos) side of the river without notice because the width of the river was larger than the detection range of the transmitter. The remaining 12 tagged fish (43%) could be detected by the receivers installed, excluding the release point receiver. Of these 12 tagged fish, six showed long-distance (30–80 km) upstream movements and one long-distance (50 km) downstream movement. These seven fish (25%) were detected only during the daytime, suggesting that the Mekong giant catfish is diurnal.

The horizontal and vertical movements of eight immature hatchery-reared Mekong giant catfish Pangasianodon gigas were monitored using acoustic telemetry in Mae Peum Reservoir, Thailand between 2003 and 2004. The fish were monitored for between eight days and more than 9 months. All of the fish moved over the entire reservoir within approximately 40 days after release. Subsequently, the home range became small approximately 40 days after release. The fish preferred deep areas in the reservoir. The fish displayed diel horizontal and vertical movement patterns. The fish showed larger-scale horizontal movement during the daytime than at night. The fish repeatedly showed active vertical movement during the day, whilst there was little variation in swimming depth at night. Our results imply that the vertical movements of the fish were related to the environmental condition of the reservoir.

The vertical movements of one Mekong giant catfish Pangasianodon gigas were monitored for 3 days in August 2004 using a depth-temperature micro data logger. The logger was recovered using an innovative time-scheduled release system and located by searching for VHF radio signals. The logger was found approximately 2.2 km away from the release point and provided (n=705,128) depth and temperature data collected over a period of 98 hours following the release. The fish spent more than 99% of its time at less than 3 m below the surface. The maximum swimming depth was 5.6 m. No sharp thermocline was present during the experiment. Temperature did not have any detectable effect on the pattern of vertical movement of the fish. The dissolved oxygen concentration (DO) was stratified, with a concentration of >60% saturation in the first 3 m below the surface falling to 10% saturation at depths lower than 4 m. This specific DO stratification was found to limit the vertical movement of the catfish.

Catfishes of the family Pangasiidae are an important group that contributes significantly to the fisheries of the Mekong River basin. In recent times the populations of several catfish species have declined, thought to be due to overfishing and habitat changes brought about by anthropogenic influences. The Mekong giant catfish Pangasianodon gigas Chevey, 1913 is listed as Critically Endangered on the IUCN Red List. In the present study, we assessed the level of genetic diversity of nine catfish species using sequences of the large subunit of mitochondrial DNA (16S rRNA). Approximately 570 base pairs (bp) were sequenced from 672 individuals of nine species. In all species studied, haplotype diversity and nucleotide diversity ranged from 0.118±0.101 to 0.667±0.141 and from 0.0002±0.0003 to 0.0016±0.0013, respectively. Four haplotypes were detected among 16 samples from natural populations of the critically endangered Mekong giant catfish. The results, in spite of the limited sample size for some species investigated, indicated that the level of genetic variation observed in wild populations of the Mekong giant catfish (haplotype diversity=0.350±0.148, nucleotide diversity=0.0009±0.0008) is commensurate with that of some other related species. This finding indicates that (1) wild populations of the Mekong giant catfish might be more robust than currently thought or (2) present wild populations of this species carry a genetic signature of the historically larger population(s). Findings from this study also have important implications for conservation of the Mekong giant catfish, especially in designing and implementing artificial breeding programme for restocking purposes.

For conservation and successful stock enhancement of endangered species, an understanding of the movement patterns and behavior of the target species is indispensable. The Mekong giant catfish, Pangasianodon gigas , is endemic to the Mekong Basin and now is threatened with extinction. Although biotelemetry using acoustic transmitters and receivers is expected to reveal its movement patterns and behavior, the most suitable attachment method for the transmitter to the catfish is unknown. In this study we examined the effects of external attachment and surgical implantation on the survival and growth of the catfish, compared with those in control individuals, in an earthen fish pond for approximately 2 months. No fish died during the experimental period. Furthermore, we found no fungal infections in any fish and no significant differences in growth rate among treatment and control fish. However, all transmitters of externally tagged fish were lost during the experimental period. In contrast, transmitters of some surgically implanted fish remained in the peritoneal cavity. In conclusion, the surgical implantation technique is suitable for long-term monitoring of the catfish.

For the conservation and successful stock enhancement of the endangered species Mekong giant catfish Pangasianodon gigas, an understanding of its movement patterns and behavior is indispensable. The Mekong giant catfish tracking project (MCTP) has been begun to measure the movements of hatchery-reared Mekong giant catfish using acoustic telemetry and bio-logging technology in the Mae peum reservoir and Mekong River. Research in the Mae peum reservoir demonstrated that fish showed distinctive diel vertical movement and the swimming depth was limited by the thermocline or dissolved oxygen stratification. Fish also displayed diel horizontal movement between inshore at night and offshore areas during the day. Researchers in the Mekong River presented the first records of upstream and downstream movement of Mekong giant catfish for up to 97 days. Fish swam upstream at a speed of 16.2 km d-1 and downstream at a speed of 7.2 km d-1 during a day. These results will contribute to plans for the species conservation and the effective stock enhancement in reservoirs and fish ponds., Organized by Graduate School of Informatics, Kyoto University ; JSPS Bangkok Liaison Office ; Japanese Society of Bio-logging Science ; Informatics Research Center for Development of Knowledge Society Infrastructure, December 13-14, 2005, Siam City Hotel, Bangkok, Thailand

We studied the feeding habits of the hatchery-reared young Mekong giant catfish released in a fish pond and Mae peum reservoir, northern Thailand. We examined the gut (stomach and intestine) contents of 5 catfish, Relative Length of Gut (RLG) of 4 catfish and plankton composition in the reservoir. The gut contents of the catfish in the fish pond consisted of a fluid like the pellets, zooplankton, phytoplankton and aquatic plants. The gut contents in the reservoir consisted of unspecified contents, zooplankton and phytoplankton. The majority of prey items were the Branchiopoda (75 % in zooplankton) and Chlorophyceae (98 % in phytoplankton) in the gut contents of the catfish in the reservoir, while the major plankton in the reservoir were copepoda including nauplius and copepodid (mean : 50 %) and eurotatorea (mean : 41 %) in zooplankton, and chrysophyceae (mean : 52 %) and chlorophyceae (mean : 38 %) in phytoplankton. It is reasonable to suppose that the catfish positively selected their major prey items if a particular prey item was found in the gut contents, contrary to the organism composition in the reservoir. However, the cuticle and the cell walls of these plankton are resistant to intestine enzymes of some fish. Furthermore, RLG of 4 catfish were greater than 1. In general, a fish is carnivorous when RLG is less than 1, while the fish is herbivorous or omnivorous when RLG is greater than 1. These results indicate that the hatchery-reared young catfish fed on the potential prey items in front of the catfish, and the catfish might not be piscivorous but planktivorous., Organized by Graduate School of Informatics, Kyoto University ; JSPS Bangkok Liaison Office ; Japanese Society of Bio-logging Science ; Informatics Research Center for Development of Knowledge Society Infrastructure, December 13-14, 2005, Siam City Hotel, Bangkok, Thailand

In order to better understand the moving behavior of Mekong giant catfish Pangasianodon gigas in a reservoir, Thailand, two catfish were monitored using Depth-Temperature data loggers (UME 190DT, Little Leonardo, Tokyo, Japan) which were attached with a brand-new time-scheduled release system. The release system automatically detached the loggers from the catfish 5 days after deployment. Then we searched for VHF radio signals and found one of the two loggers approximately 2.2 km away from the release point. The other was never found because it was hidden by a dense cover of floating waterweeds. The logger that was recovered provided depth and temperature data for approximately 98 hours. Results from the data analyses found that the fish spent more than 99 % of their time above the depth of 3 m. The fish showed active vertical movement during the daytime but remained inactive during the nighttime (especially midnight). The fish made only 8 deep vertical movements greater than 4.8 m and the maximum swimming depth was 5.6 m. The differences in the ambient temperatures during these movements were less than 2.0℃. The stable temperature might have little effect on the catfish behavior. During our experiment period, there was no thermocline although DO stratification was built up at the depth of 4 m, and the DO below 4 m deep was uniformly less than 10 %. These results indicated that the DO stratification might limit the vertical movement of the catfish. Furthermore, in 8 deep movements the descent rates were significantly lower than the ascent rate for each movement, respectively, which indicated that the fish might display the avoidance movement from the hypoxic waters., Organized by Graduate School of Informatics, Kyoto University ; JSPS Bangkok Liaison Office ; Japanese Society of Bio-logging Science ; Informatics Research Center for Development of Knowledge Society Infrastructure, December 13-15, 2004, Imperial Tara Hotel, Bangkok, Thailand

In order to recapture Mekong giant catfish, we developed an automatic fish recapture system (AFR system). The AFR system causes the free-ranging fish to float at the scheduled time. We have conducted experiments on Mekong giant catfish in the Mae peum reservoir, Thailand. We used 7 cultivated young catfish, whose total length ranged from 76.5 cm to 86.5 cm. After we attached the AFR system to the catfish, we released them into the reservoir in August (one catfish), October (three catfish) and December (three catfish) of 2004. The AFR systems were scheduled to cause the catfish to float after four to eight days. The recovery percentage of both the catfish and the AFR systems was 43 %. The recovery percentage of only the AFR systems was 29 %. The percentage of loss of all the catfish and the AFR systems was 29 %. We also examined the stomach contents of the catfish with a microscope and found some zooplankton and phytoplankton. The total number of the zooplankton in the stomach contents in October was 1288 individuals and the most, and those in August and December were 33 and 34 individuals respectively and least., Organized by Graduate School of Informatics, Kyoto University ; JSPS Bangkok Liaison Office ; Japanese Society of Bio-logging Science ; Informatics Research Center for Development of Knowledge Society Infrastructure, December 13-15, 2004, Imperial Tara Hotel, Bangkok, Thailand

Annual sex hormonal profiles, gonad development and age determination of 18 (13–14 kg body weight) and three (145–226 kg body weight) Mekong giant catfish (MGC) (Pangasianodon gigas, Chevey) reared in earthen ponds in Chiang Mai and from the Mekong River in Chiang Rai, Thailand, respectively, were investigated. The hormonal profiles were determined from blood samples of the fish by electrochemiluminescence immunoassay during May to August in 2000. The highest testosterone levels of 0.06 ng mL−1 in both sexes and the highest oestradiol of 47.8 and 14.23 pg mL−1 in females and males, respectively, were observed in May. The gonadosomatic index was found to be 0.07 for males and 0.38 for females from ponds in comparison with 2.27 for males and 8.29 for females from the Mekong River. Higher development stages of spermatocytes and oocytes of the cultured fish in May than in February and November were demonstrated. No mature germ cells were obtained from either the males or females, indicating no sexual maturity. The average age of fish was determined from the annual rings of the cross-section of the pectoral fins by a stereomicroscope. The average age of fish in earthen pond determined from the annual ring was 8 years, which agreed with the actual culture records, while those from the Mekong River were 21 years. This information will be beneficial for the breeding programmes and conservation of the MGC.

Mekong giant catfish is one of the largest freshwater catfish in the world. It is endemic to the Mekong basin, and is endangered species. We have studied the Mekong giant catfish to conserve and enhance its resource by biotelemetry since 2001. In the Mae peum Reservoir in 2003, we found that the catfish vertically moved down only above the thermo cline in the daytime and up to the surface layer in the nighttime daily. This diel vertical movement appears to be related to the foraging behavior. However, the foraging behavior and prey items of the catfish are still unknown. One of the methods to clarify the foraging behavior and the prey items is to examine the stomach contents of the catfish in the daytime and the nighttime respectively. In order to examine the stomach contents transition hourly, we must be able to recapture the catfish at any time. Therefore, we made a plan to develop the new device named an Automatic Fish Recapture System (AFR System) to recapture the free swimming fish at the set time. And we will apply this device to the catfish and examine the stomach contents of the catfish and simultaneously study the migration of the catfish by incorporating with the biotelemetry system. Consequently, we will clarify the foraging behavior and the prey items of the catfish. In this paper, the outline of the AFR System and study plan of the catfish using this system is introduced., Organized by Graduate School of Informatics, Kyoto University ; Fisheries Laboratory of Kinki University ; JSPS Bangkok Liaison Office ; Informatics Research Center for Development of Knowledge Society Infrastructure, December 11-13, 2003, Bangkok, Thailand

Mekong giant catfish Pangasianodon gigas is endangered species. It is urgently necessary to learn more about the movement pattern of the catfish to conserve. We started the Mekong giant Catfish Tracking Project (MCTP) that is ecological research cooperative with Thai government at 2001. In this paper, the first results of MCTP are introduced. Horizontal and vertical movements of Mekong giant catfish were determined using pressure-sensitive ultrasonic transmitters in the reservoir. We found the clear daily movement patterns of the catfish. The catfish appeared to favor relatively deep areas and had 2-3 km excursions at night. The catfish exhibited the ascent to the surface at dusk and the descent to the thermocline at dawn in the reservoir. These behaviors of the catfish might be related to the feeding behavior., Organized by Graduate School of Informatics, Kyoto University ; Fisheries Laboratory of Kinki University ; JSPS Bangkok Liaison Office ; Informatics Research Center for Development of Knowledge Society Infrastructure, December 11-13, 2003, Bangkok, Thailand

Juveniles of the Mekong giant catfish, Pangasianodon gigas (Teleostei), have 3 sorts of tooth-upper and lower jaw teeth, palatal teeth, and pharyngeal teeth--but adults are toothless. To investigate the histogenesis and disappearance of the teeth, we made serial sections of the mouth and teeth of juvenile fish at 10 developmental stages (from ca. 8.5 to ca. 30 cm in total length) and examined them under scanning electron microscope and light microscope. Observations of teeth and surrounding tissues in the serial sections revealed the process of tooth resorption by active odontoclast-like cells. Numbers of jaw and palatal teeth decreased with age. When the fish reached ca. 14 cm in total length, the numbers of functional upper jaw teeth and successional tooth germs decreased rapidly, and the developmental rate of successional tooth germs slowed. When the fish reached ca. 24 cm, no teeth existed in the upper jaw. It is clear that tooth disappearance results from the shedding of functional teeth and the lack of replacement tooth germs.

Temperature and depth data logger was attached to Mekong giant catfish to observe their swimming behavior in a rearing pond. Four artificial seed reared in the Karasin Freshwater Research Station, Thailand were used to obtain the body temperature and fish position on water depth. The fish were anesthetized and implanted with a data logger (DST milli, Star-oddi Co., Iceland) into the body cave on 2 May 2002. One data logger was retrieved and body temperature and depth data were obtained for about one month. The fish moved to relatively deeper layer after sunrise and stayed there in the morning. In the afternoon the fish became active gradually and began to move vertically. After sunset the fish got more active and moved vertically from the surface to the bottom of the pond until the next sunrise. At sunrise the fish stopped the vertical movement. It seems that Mekong giant catfish have a nocturnal characteristic and get most active at twilight., Southeast Asia Sea Turtle Associative Research, Bangkok, Thailand, 16-19 December 2002

The Mekong giant catfish Pangasianodon gigas is endemic to the Mekong River basin, and is recognized as endangered species, largely due to overfishing and development of the river basin. We monitored food intake of P. gigas in a stable environment in an aquarium over a 6-year period and analyzed their feeding rhythm and fasting periods. The daily food intake for each fish was recorded from 18 June 2004 to 17 June 2010. The feeding rhythm or pattern was determined by the fast Fourier transform (FFT) analysis. The FFT analysis revealed that different cycles of feeding rhythm (168.8, 313.1, and 365.3 days) in three catfishes and no observable cycles in two catfishes. However, three catfishes showed subordinate peaks with approximately 365 days (365.3 days for all). These suggest that, at least, four of five catfish had have approximately 365-days feeding cycle. We also showed that all catfish undergo long-term fasting periods (> 20 days). Of note, the feeding/fasting pattern coincides with the wet/dry seasons in Thailand, which also corresponds to the abundance of the catfish food resource (Cladophora spp.). We found that P. gigas exhibit a seasonal feeding rhythm that is synchronized by food availability. Furthermore, we found that the seasonal feeding rhythm was gradually dampened over time, suggesting that the observed seasonal feeding rhythm with long-term fasting of the catfish is likely controlled by an endogenous clock system. To our knowledge, this is the first case of quantification of the seasonal feeding rhythm with fasting periods in teleost fish.

We are performing the Southeast Asia sea turtle associative research (SEASTAR2000), the Mekong giant catfish tracking project (MCTP) and the dugong biological survey (DBS) as part of the 21st Century Center of Excellence (COE) Program (2002-2007) and the Global COE Program (2007-2012). All the species of the projects are heavily endangered and need sufficient degree of protection. They are listed in the Convention on International Trade in Endangered Species (CITES) Appendix I. However, very little is known of the species whilst the implementation of their conservation is a pressing problem in Thailand and neighboring ASEAN countries. Field informatics with bio-logging including satellite telemetry, ultrasonic telemetry, GPS and advanced data-loggers will be a powerful tool to clarify the ecology of the endangered species in order to realize co-existence between human beings and the endangered species.

We performed international studies at the COE Bangkok office established by the Informatics Research for Development of Knowledge Society Infrastructure in Thailand, The projects include the Southeast Asia sea turtle associative research (SEASTAR2000), the Mekong giant catfish tracking project (MCTP) and the dugong biological survey (DBS). All the species of the projects are heavily endangered and need a sufficient degree of protection. Very little is known of these species whilst the implementation of conservation measures is a pressing problem in Thailand and neighboring ASEAN countries. In these countries, the conservation policy sometimes poses some troubles because the area to be protected is also fishing ground where the local people live. We must appreciate the need for coexistence between the endangered species and the local people based on scientific knowledge

The Mekong giant catfish (Pangasianodon gigas) is the largest scale-less freshwater fish of the world, and a critically endangered species. We determined the complete nucleotide sequence (16,533 bp) of the mitochondrial genome of the Mekong giant catfish, and conducted phylogenetic analyses based on mitochondrial protein (the combined amino acid sequences of all 13 mitochondrial protein coding genes) and rRNA (the combined nucleotide sequences of mitochondrial 12S and 16S rRNA genes) data sets in order to further clarify the relative phylogenetic position of P. gigas, and to recover phylogenetic relationships among 15 out of the 33 families of Siluriformes. Phylogenetic analyses (maximum parsimony, minimum evolution, maximum likelihood, Bayesian inference) of the protein data set were congruent with a basal split of the order into Loricarioidei and Siluroidei, and supported a closer relationship of the Mekong giant catfish (family Pangasiidae) to Siluridae than to Bagridae. The rRNA-based Bayesian phylogeny recovered Callichthyidae as the sister group of all other analyzed non-diplomystid catfish families, rendering Loricarioidei paraphyletic. In addition, Loricariidae were recovered as paraphyletic due to the inclusion of Astroblepidae. However, none of the two relationships received bootstrap support in the maximum parsimony, minimum evolution, and maximum likelihood analyses, and should be interpreted with caution. The derived position of Cetopsidae within Siluroidei, the sister group relationship of Pseudopimelodidae and Pimelodidae, and a close relationship of Doradidae and Auchenipteridae to the exclusion of Mochokidae were strongly supported. Pangasiidae was placed as a single lineage without clear affinities.

We are performing the Southeast Asia sea turtle associative research (SEASTAR2000), the Mekong giant catfish tracking project (MCTP) and the dugong biological survey (DBS) as one of the 21st Century Center of Excellence Programs, 2002-2007. All the species of the projects are heavily endangered and need a sufficient degree of protection. Whilst very little is known of the species the need to implement conservation is a pressing problem in Thailand and neighbouring ASEAN countries. The conservation policy sometimes poses troubles because the area to be protected is also a fishing ground where the local people live. We must appreciate the need for coexistence between the endangered species and the local people based on our scientific knowledge., Organized by Graduate School of Informatics, Kyoto University ; JSPS Bangkok Liaison Office ; Japanese Society of Bio-logging Science ; Informatics Research Center for Development of Knowledge Society Infrastructure, December 13-14, 2005, Siam City Hotel, Bangkok, Thailand